Design is an important piece of creating that perfect web site for yourself or for your customers. Design is a pretty large field because it can cover everything from image design, to designing the right layout within your markup and CSS. To the right you will see some of my favorite books, that I recommend reading. They will give you a good starting point in designing web sites that are good looking and functional at the same time.
There are many tools out there that produce some great results. I started my graphical design using that ever popular free tool called GIMP. GIMP did me good for about a year and then the company I work for ordered me a copy of Adobe Photoshop CS2, and I haven't looked back. It is not that GIMP failed me in any way, but it was ten times easier to find Photoshop tutorials than it was GIMP tutorials. This in my opinion is very important, because I don't always have a lot of time to figure out things on my own between all the projects I have going on. Having said that though, I do enjoy the discovery process and teaching myself through trial and error, but sometimes you just don't have time to do that.
As this site grows, I will be providing my own Photoshop tutorials, and maybe even some GIMP guides. Any time I add a new guide or tutorial, I will be sure to post it in the CornerPixel Blog, so make sure to check out the RSS for the blog so you can keep up to date with CornerPixel.
When it comes to a good layout design there are a few things you have to consider. Of course the graphical images, but also how and where they will be displayed on the page. This is important because it will effect your markup and CSS. I am usually in the mind set that anything is possible, but as you design your site you have to make sure that your design won't be possible in only such away that it will require loads of extra markup and loads of extra styles just to get it to work. I love The Zen of CSS Design book for help with that. Also a good site that I recommend to anyone interested in designing a good flexible web site is www.csszengarden.com.
Another thing to think about is flexibility. How well will the site you are designing go through a redesign in two years, or whenever the customer decides they just want it to look different. (Oh yeah that happens a LOT) Designing a good standards compliant site will help a lot with that. CSS can be such a big help if used correctly. In the future I will have guides for good CSS practices under the {standards} menu so keep an eye on the RSS feed for new updates.
A few books I recommend if you are interested in good Design, both graphical and layout.